Methods and apparatus for estimating digital pre-distortion coefficients

Abstract

In an embodiment, a method includes: providing a first set of coefficients to a digital pre-distortion (DPD) corrector, the DPD corrector receiving a input signal having a first profile, the first set of coefficients being associated with the first profile; in response to detecting a change in a profile of the input signal from the first profile to a second profile, extracting, in response to an output signal converging to the input signal, a second set of coefficients corresponding to the second profile, the output signal being based on an output of the DPD corrector; and generating a third set of coefficients based on the first and second sets of coefficients, the third set being different from the first and second sets.

What is claimed is: 
     
         1 . A method comprising:
 providing a first set of coefficients to a digital pre-distortion (DPD) corrector, the DPD corrector receiving a input signal having a first profile, the first set of coefficients being associated with the first profile;   in response to detecting a change in a profile of the input signal from the first profile to a second profile, extracting, in response to an output signal converging to the input signal, a second set of coefficients corresponding to the second profile, the output signal being based on an output of the DPD corrector; and   generating a third set of coefficients based on the first and second sets of coefficients, the third set being different from the first and second sets.   
     
     
         2 . The method of  claim 1 , further comprising, in response to detecting a change in a profile of the input signal from the second profile to a third profile, providing the third set of coefficients to the DPD corrector for a first period of time. 
     
     
         3 . The method of  claim 2 , further comprising:
 after the first period of time and in response to the output signal converging to the input signal, extracting a fourth set of coefficients corresponding to the third profile; and   updating the third set of coefficients based on the fourth set of coefficients.   
     
     
         4 . The method of  claim 1 , further comprising:
 extracting, in response to the output signal converging to the input signal, a correlation matrix associated with an amplifier outputting the output signal; and   generating the third set of coefficients based on the correlation matrix.   
     
     
         5 . The method of  claim 4 , wherein the correlation matrix represents correlations between different nonlinear terms in a model used to correct nonlinearities of the amplifier. 
     
     
         6 . The method of  claim 1 , further comprising monitoring an error between the output signal and the input signal to determine when the output signal converges with the input signal. 
     
     
         7 . The method of  claim 1 , wherein convergence between the input signal and the output signal occurs after at least two iterations of pre-distorting the input signal by the DPD corrector. 
     
     
         8 . The method of  claim 1 , further comprising:
 detecting that the input signal changed from the first profile to a third profile over a period of time, the period of time greater than a time it takes for the output signal to converge with the input signal;   providing the third set of coefficients to the DPD corrector for a first period of time corresponding to a first iteration of pre-distorting the input signal;   generating a fourth set of coefficients in response to the output signal being adjusted based on the third set of coefficients; and   providing the fourth set of coefficients to the DPD corrector for a second time period corresponding to a second iteration of pre-distorting the input signal.   
     
     
         9 . The method of  claim 8 , further comprising:
 waiting for the output signal to converge with the input signal;   extracting, in response to the output signal converging to the input signal, a fifth set of coefficients corresponding to the third profile; and   updating the third set of coefficients based on combining the third set of coefficients with the fifth set of coefficients.   
     
     
         10 . The method of  claim 1 , wherein the second set of coefficients is a projected coefficient vector, the method further comprising extracting a subset of matrices and a subset of projected coefficient vectors corresponding to a plurality of profiles. 
     
     
         11 . The method of  claim 10 , further comprising combining subsets of the matrices and subsets of the projected coefficient vectors for the plurality of profiles to generate the third set of coefficients. 
     
     
         12 . The method of  claim 1 , wherein the third set of coefficients is an updated third set of coefficients, the method further comprising:
 comparing a first time and temperature with a second time and temperature corresponding to the updated third set of coefficients; and   removing the third set of coefficients from memory when the comparison returns a threshold difference between the first time and temperature and second time and temperature.   
     
     
         13 . The method of  claim 12 , wherein the first time corresponds a first timestamp of when the third set of coefficients was updated, the second time corresponds to a second timestamp of when the third set of coefficients was generated. 
     
     
         14 . The method of  claim 13 , wherein the first temperature corresponds to a temperature of a power amplifier providing the output signal at the first timestamp and the second temperature corresponds to the temperature of the power amplifier at the second timestamp. 
     
     
         15 . A method comprising:
 detecting a profile change in an input signal;   selecting, in response to the profile change, a first coefficient corresponding to a first profile type of the input signal to pre-distort the input signal during a first iteration of digital pre-distortion correction; and   generating a regularization vector based on at least one converged coefficient corresponding to a second profile type different than the first profile type of the first coefficient; and   estimating a second coefficient for pre-distorting the input signal during a second iteration based on the regularization vector.   
     
     
         16 . The method of  claim 15 , wherein the first profile type corresponds to a signal with a first power level, and wherein the second profile type corresponds to a signal with a second power level that is lower than the first power level. 
     
     
         17 . The method of  claim 16 , wherein the regularization vector is used to regularize the second coefficient with the converged coefficient generated for the second profile type. 
     
     
         18 . The method of  claim 15 , wherein the converged coefficient is a first converged coefficient, the method further comprising:
 obtaining a second converged coefficient corresponding to a third profile type;   determining an average of the first converged coefficient and the second converged coefficient; and   generating the regularization vector based on the average of the first converged coefficient and the second converged coefficient.   
     
     
         19 . The method of  claim 15 , further comprising generating the regularization vector based on converged coefficients corresponding to a plurality of profile types except the first profile type. 
     
     
         20 . The method of  claim 15 , wherein the converged coefficient is a first converged coefficient, the method further comprising:
 determining the input signal changed from a third profile type to a fourth profile type;   in response to the profile change from the third profile type to the fourth profile type, waiting for an output signal to converge with the input signal;   extracting, in response to the output signal converging to the input signal, a second converged coefficient corresponding to the converged output signal and the fourth profile type;   generating a profile agnostic coefficient based on combining the first converged coefficient and the second converged coefficient; and   generating the regularization vector based on the profile agnostic coefficient, wherein during the second iteration of digital pre-distortion, the profile agnostic coefficient is used to regularize the second coefficient.